I bought the parts for my rig around July, before the DDR3 market went haywire and the prices rose to what they are today. Snagged all 6GB for $92 CAD off NCIX. I knew I should have got a dual channel kit, but at the price it was hard to resist 6GB.

Initially:
I had 3 sticks in the first 3 DIMMs. I ran them at 1.6V, DDR3-1600 (x8 multi, 200FSB) and 9-9-9-24 timings, unganged and in single channel (didn't really have a choice there). I never bothered to try for more. As time went on with my rig I realised three things:
1) There is no way I will ever need all 6GB
2) Dual channel has got to be better than single channel
3) Leaving my hardware on auto and not optimizing them was not a great idea

I was planning on getting rid of my i7 kit and getting a dual channel kit instead but I decided to play with them tonight.

Results:
I first took out one of the sticks. Both sticks (2x2GB) are now in the DIMMs closest to the CPU. I managed to hit 1333MHz (x6.66) at 7-8-7-20 timings, 2T, with 1.4V NB and 1.45V CPU NB VID. Dual channel + unganged. Memtest86 passed a few minutes ago so I'm good to go with these speeds/timings.

Yeah, RAM is RAM, so 2 sticks from a triple channel kit will work as a dual channel kit. However, I was more surprised at how well these sticks that were designed for the i7 platform did in my rig. I have a C2 X3 720, and C2 Phenoms are notoriously picky with RAM.